8. Transfer to a 10 per cent aqueous solution of sodium hyposulphite for a few minutes. 9. Wash in water; dehydrate in alcohol; clear in oil of cajuput; xylol; balsam. Axis-cylinders, intracellular fibrils and Golgi’s network are stained. 4. =STAINING OF NEURO-FIBRILLAR STRUCTURES.= These are stained by Bielschowsky’s method, and by acid fuchsin after fixation with osmic acid. The special methods (Apathy’s gold method, Bethe’s molybdic method, the silver methods of Ramen y Cajal and Robertson) have little practical application in pathologic work, and are used chiefly in the study of normal histology. 5. =THE STAINING OF NEUROGLIA.= A. Weigert’s Method. 1. Fix small pieces of fresh tissue in 10 per cent formol for 24 hours. 2. Mordant. 8 days at room temperature (4 days at 37°C.) in copper acetate 5 grms., fluorchrom 2.5 grms., acetic acid 5 cc., water 100 cc. Or, harden and mordant at the same time in 9 parts of the copper mordant, and 1 part of commercial formol for 8 days, changing on the second day, and once again later. 3. Wash in water: after-harden in alcohol; imbed in celloidin; cut. 4. Place sections in ⅓ per cent aqueous solution of potassium permanganate. 5. Wash in two changes of water. 6. Place in the following reducing mixture, 2-4 hours: Chromogen 5 grms., formic acid (sp. gr. 1.2) 5 cc., water 100 cc.; filter; to 90 cc. add 10 cc. of 10 per cent sodium sulphite solution just before using. 7. Wash twice in water. 8. Place sections in 5 per cent carefully filtered aqueous chromogen solution 10-12 hours. (The glia fibres become darker, and a yellowish contrast is obtained for the ganglion and ependymal cells and thicker axis cylinders. Connective-tissue is stained red.) 9. Wash in water. 10. Place section on a slide freshly cleaned with alcohol; dry with filter paper; stain in the following mixture for about 30 seconds: Saturated solution of methyl violet in 70-80 per cent alcohol 100 cc., oxalic acid 5 per cent solution, 5 cc. 11. Remove excess of stain; dry with filter paper; cover slide with saturated solution of iodine in 5 per cent potassium-iodide solution, 30 seconds. 12. Remove iodine solution; dry with filter paper; differentiate in a mixture of equal parts aniline oil and xylol until no more heavy clouds of stain are given off. Control under microscope. 13. Dry section with filter-paper; add xylol; blot; repeat three times. 14. Mount in balsam or turpentine colophonium. Neuroglia fibres and nuclei, blue; connective-tissue, blue-violet; thicker myelin sheaths, ganglion and ependymal cells, yellowish. This is the best method, none of the modifications giving as good results. No method, however, will stain every neuroglia-fibre. B. Mallory’s Neuroglia Method.